Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a nacelle mounted atop the tower, a generator positioned in the nacelle, and one or more rotor blades coupled to a hub. The one or more rotor blades convert kinetic energy of wind into mechanical energy using known airfoil principles. A drivetrain transmits the mechanical energy from the hub to the generator. The generator then converts the mechanical energy to electrical energy that may be supplied to a utility grid.
The orientation of the rotor blades may be adjustable to control the amount of kinetic energy extracted from the wind. More specifically, the rotor blades may be rotatably coupled to the hub. In this respect, a pitch drive mechanism may rotate each rotor blade about a corresponding pitch axis to adjust a pitch angle of thereof. As such, the pitch angles of the rotor blades may be adjusted between a feathered position where a minimum amount kinetic energy extracted from the wind and a power position where a maximum amount kinetic energy extracted from the wind.
The pitch drive mechanisms may adjust the pitch angles of the rotor blades to control the loads exerted on the rotor blades by the wind and other atmospheric conditions. For example, when the rotor blades experience high wind velocities, the pitch angles of the rotor blades may be adjusted toward the feathered position to reduce the loads thereof. When the wind velocities decrease, the pitch angles of the rotor blades may be adjusted back toward the power position.
The wind velocities experienced by the rotor blades may vary depending on the rotational position of the rotor blades relative to the nacelle. As such, the loads of the rotor blades may also vary with rotational position. In this respect, the pitch drive mechanisms may adjust the pitch angles of the rotor blades toward the feathered position to reduce the loads thereof when the rotor blades are positioned in rotational positions where high wind velocities are present. The pitch drive mechanisms may then adjust the rotor blades toward the power position when the rotor blades leave the rotational positions where high wind velocities are present. In certain instances, the pitch drive mechanisms may not be capable of adjusting the pitch angles of the rotor blades quickly enough to compensate for the changes in wind velocity. As such, the pitch drive mechanisms may become saturated and may experience significant wear.
Accordingly, improved wind turbines, and, in particular, improved systems and methods for reducing loads of wind turbine rotor blades, are desired in the art. Specifically, systems and methods that do not saturate the pitch drive mechanisms and produce relatively less wear on the wind turbine would be advantageous.